1. Technical Field
The present invention relates to a stepping motor control circuit and an analogue electronic timepiece using the stepping motor control circuit.
2. Description of the Related Art
In the related art, in an analogue electronic timepiece or the like, a stepping motor including a stator having a rotor storage hole and a positioning portion for determining a stop position of a rotor, the rotor disposed in the rotor storage hole, and a coil, in which the rotor is rotated and the rotor is stopped at a position corresponding to the positioning portion by causing the stator to generate a magnetic flux by supplying alternating signals to the coil is used.
A method employed as a method of controlling the stepping motor is a correction driving system in which whether the stepping motor is rotated or not is detected by detecting an induced signal corresponding to an induced voltage generated in the stepping motor when the stepping motor is driven by a main driving pulse, and the stepping motor is driven by a main driving pulse having a different pulse width or is forcedly rotated by a correction driving pulse having the pulse width larger than that of the main driving pulse according to the result of detection of whether or not the stepping motor is rotated (for example, see JP-B-61-15385).
In WO2005/119377, when detecting the rotation of the stepping motor, a unit for comparing and determining a detected time and a reference time in addition to the detection of the induced signal is provided and, after having rotated the stepping motor with a main driving pulse P11, if the induced signal is lower than a predetermined reference threshold voltage Vcomp, a correction driving pulse P2 is outputted and the main driving pulse P1 for the next time is changed to a main driving pulse P12 having a larger energy the main driving pulse P11 for driving. When the detection time when rotating the rotor with the main driving pulse P12 is earlier than the reference time, the main driving pulse P12 is changed to the main driving pulse P11, and the rotation is made with a main driving pulse P11 according to a load during the drive, so that the current consumption is reduced.
However, there is a problem such that a time of the day when a peak of the induced signal occurs due to free vibrations of the rotor is affected by gear train load fluctuations, and variations in peak voltage increase in proportion to the elapse of time.
Since variations in load exist in individual movements, there arises a problem such that it is difficult to perform a stable driving pulse control on the basis of a peak occurrence time of the induced signal.